Transaction systems, including, for example, banking systems and/or securities trading systems, may include back end applications that perform logic that may be necessary to conduct transactions. A front end of these systems may be designed for presentation and ease of use and may enable one or more users to input information. The front end of these systems may call one or more applications in the back end in order to execute the logic to conduct the transaction. In some situations, these back end systems may be difficult to test because there may not be a user interface through which to access them.